/*
 * Copyright  2000-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); 
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License. 
 *
 */
package org.apache.bcel.generic;

import java.io.DataOutputStream;
import java.io.IOException;
import org.apache.bcel.Constants;
import org.apache.bcel.ExceptionConstants;
import org.apache.bcel.classfile.ConstantPool;
import org.apache.bcel.util.ByteSequence;

/** 
 * INVOKEINTERFACE - Invoke interface method
 * <PRE>Stack: ..., objectref, [arg1, [arg2 ...]] -&gt; ...</PRE>
 *
 * @version $Id: INVOKEINTERFACE.java 386056 2006-03-15 11:31:56Z tcurdt $
 * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 */
public final class INVOKEINTERFACE extends InvokeInstruction {

    private int nargs; // Number of arguments on stack (number of stack slots), called "count" in vmspec2


    /**
     * Empty constructor needed for the Class.newInstance() statement in
     * Instruction.readInstruction(). Not to be used otherwise.
     */
    INVOKEINTERFACE() {
    }


    public INVOKEINTERFACE(int index, int nargs) {
        super(Constants.INVOKEINTERFACE, index);
        length = 5;
        if (nargs < 1) {
            throw new ClassGenException("Number of arguments must be > 0 " + nargs);
        }
        this.nargs = nargs;
    }


    /**
     * Dump instruction as byte code to stream out.
     * @param out Output stream
     */
    public void dump( DataOutputStream out ) throws IOException {
        out.writeByte(opcode);
        out.writeShort(index);
        out.writeByte(nargs);
        out.writeByte(0);
    }


    /**
     * The <B>count</B> argument according to the Java Language Specification,
     * Second Edition.
     */
    public int getCount() {
        return nargs;
    }


    /**
     * Read needed data (i.e., index) from file.
     */
    protected void initFromFile( ByteSequence bytes, boolean wide ) throws IOException {
        super.initFromFile(bytes, wide);
        length = 5;
        nargs = bytes.readUnsignedByte();
        bytes.readByte(); // Skip 0 byte
    }


    /**
     * @return mnemonic for instruction with symbolic references resolved
     */
    public String toString( ConstantPool cp ) {
        return super.toString(cp) + " " + nargs;
    }


    public int consumeStack( ConstantPoolGen cpg ) { // nargs is given in byte-code
        return nargs; // nargs includes this reference
    }


    public Class[] getExceptions() {
        Class[] cs = new Class[4 + ExceptionConstants.EXCS_INTERFACE_METHOD_RESOLUTION.length];
        System.arraycopy(ExceptionConstants.EXCS_INTERFACE_METHOD_RESOLUTION, 0, cs, 0,
                ExceptionConstants.EXCS_INTERFACE_METHOD_RESOLUTION.length);
        cs[ExceptionConstants.EXCS_INTERFACE_METHOD_RESOLUTION.length + 3] = ExceptionConstants.INCOMPATIBLE_CLASS_CHANGE_ERROR;
        cs[ExceptionConstants.EXCS_INTERFACE_METHOD_RESOLUTION.length + 2] = ExceptionConstants.ILLEGAL_ACCESS_ERROR;
        cs[ExceptionConstants.EXCS_INTERFACE_METHOD_RESOLUTION.length + 1] = ExceptionConstants.ABSTRACT_METHOD_ERROR;
        cs[ExceptionConstants.EXCS_INTERFACE_METHOD_RESOLUTION.length] = ExceptionConstants.UNSATISFIED_LINK_ERROR;
        return cs;
    }


    /**
     * Call corresponding visitor method(s). The order is:
     * Call visitor methods of implemented interfaces first, then
     * call methods according to the class hierarchy in descending order,
     * i.e., the most specific visitXXX() call comes last.
     *
     * @param v Visitor object
     */
    public void accept( Visitor v ) {
        v.visitExceptionThrower(this);
        v.visitTypedInstruction(this);
        v.visitStackConsumer(this);
        v.visitStackProducer(this);
        v.visitLoadClass(this);
        v.visitCPInstruction(this);
        v.visitFieldOrMethod(this);
        v.visitInvokeInstruction(this);
        v.visitINVOKEINTERFACE(this);
    }
}
